Catheters for the introduction or removal of fluids may be located in various venous locations and cavities throughout the body of a patient for introduction of fluids to the body or removal of fluids from the body. Such catheterization may be performed by using a single catheter having multiple lumens. A typical example of a multiple lumen catheter is a dual lumen catheter in which one lumen introduces fluid and the other lumen removes fluid. An example of such a catheter assembly is the ASH SPLIT-CATH® catheter. Catheterization may also be performed by using separate, single lumen catheters inserted through two different incisions into an area to be catheterized. An example of such a catheter assembly is a TESIO® catheter.
Generally, to insert any catheter into a blood vessel, the vessel is identified by aspiration with a long hollow needle in accordance with the well known Seldinger technique. When blood enters a syringe attached to the needle, indicating that the vessel has been found, a thin guide wire is then introduced, typically through a syringe needle or other introducer device into the interior of the vessel. The introducer device is then removed, leaving the end portion of the guide wire that has been inserted into the vessel within the vessel, and the opposing end of the guide wire projecting beyond the surface of the skin of the patient. At this point, several options are available to a physician for catheter placement. The simplest is to pass a catheter into the vessel directly over the guide wire. The guide wire is then removed, leaving the catheter in position within the vessel. However, this technique is only possible in cases where the catheter is of a relatively small diameter, made of a stiff material, and not significantly larger than the guide wire. For example, this technique may be used to insert small diameter dual lumen catheters into a patient. If the catheter to be inserted is significantly larger than the guide wire, a dilator device is passed over the guide wire to enlarge the hole. The dilator device is then removed, and the catheter is then passed over the guide wire into the vessel. The guide wire is then removed.
For chronic catheterization, in which the catheter is intended to remain inside the patient for an extended period of time, such as for weeks or even months, it is typically desired to subcutaneously tunnel the catheter using various tunneling techniques. The catheter is typically tunneled into the patient prior to inserting the catheter into the patient's vein. The catheter typically includes a cuff on the exterior of a portion of the catheter lumen that is inserted partially through, but remains in, the tunnel. The cuff is generally constructed from a fabric material, such as DACRON®, to allow the subcutaneous tissue forming the tunnel to grow into the cuff, thus securing the cuff and the catheter within the tunnel. Examples of such cuffs are disclosed in U.S. Pat. Nos. 5,509,902, 5,599,311, and 5,944,732, all of which are incorporated herein by reference. However, the cuff typically extends from the exterior of the lumen rather abruptly, which may lead to contusions or tears at the entrance to or along the tunnel, causing injury to the patient. The abrupt change also causes significant resistance to the passage of the catheter. It would be beneficial to provide a device that provides a gradual expansion between the catheter lumen and the cuff, in order to reduce the risk of injury to the patient.